On Dec. 3, 1999, six firefighters were killed in a five-story blaze that roared through an industrial building in Worcester, Mass. Two of the firefighters went into the maze-like, brick structure to scout out flames shortly after the fire began. They radioed for help after becoming disoriented, and four others who went in to rescue them became trapped as well. In a separate incident in Kansas City, Mo., a fire department lost a battalion chief when he became lost and disoriented in a fire in a large paper warehouse. These stories and others offer dramatic examples of situations in which first responders need to know where they are indoors.
GNSS receivers, which are becoming ubiquitous in personal navigation systems, often do not work well indoors, in mines, under dense foliage, in shopping malls, in airport terminals, or in other situations where a clear view of satellites is blocked. Thus, alternate systems are needed for indoor navigation.
Reverse RFID location is a technique in which fixed locations in a building are tagged with RFID tags. A person with an RFID reader can read the tags to discover where he is. Existing reverse RFID systems rely on a database of RFID tag data. A mobile tag reader queries the database to provide location and other information associated with particular RFID tag ID numbers.
While existing reverse RFID location systems are promising, there is still much room for improvement.